The present disclosure relates to a memory element and a memory device that can store therein binary or multivalued information including values greater than binary in response to a change of electrical characteristics observed in a memory layer including an ion source layer.
As a nonvolatile memory from which information is not erased even if power is turned off, previously proposed are a flash memory, a FeRAM (Ferroelectric Random Access Memory), an MRAM (Magnetoresistive Random Access Memory), and others, for example. Such types of memories enable to keep any written information for a long time with no supply of power. However, such types of memories each have advantages and disadvantages. In other words, the flash memory is high in packaging density, but is disadvantageous in terms of operation speed. The FeRAM has the limitations for micromachining to achieve a higher packaging density, and also has a problem in a manufacturing process. The MRAM has a problem of power consumption.
In consideration thereof, proposed is a memory element of a new type being especially advantageous considering the limitations of micromachining of memory elements. This memory element is in the configuration in which two electrodes sandwich therebetween an ion conductor including specific metal. With such a memory element, one of the two electrodes is configured to include metal same as that included in the ion conductor. This allows, at the time of voltage application between the two electrodes, dispersion of the metal in the electrode into the ion conductor as ions, thereby changing the resistance value of the ion conductor or the electrical characteristics such as capacitance. As an example, Patent Literature 1 and Non-patent Literature 1 each describe the configuration of a memory device utilizing such characteristics. Especially Patent Literature 1 proposes to configure an ion conductor by a solid solution of chalcogenide and metal. To be specific, it is made of a material being AsS, GeS, or GeSe, having solid solution of Ag, Cu, or Zn, and one of the two electrodes is configured to include Ag, Cu, and Zn.